Time delay device



Nov. 12, 1963 T. P. FARKAS TIME DELAY DEVICE Original Filed Sept. 2l, 1956 :INVEN P THOMAS l? FAR 4 uSy/w/M AGENT United States Patent O N' 3,110,229 'EWE DELAY DEVICE Thomas l?. Farkas, Bloomfield, Conn., assigner to United Aircraft Corporation, East Hartford, Conn., a corporation of lelaware @riginal application Sept. 2l, 1956, Ser. No. 611,337. Bivided and this application Aug. 25, 1966, Ser. No. 51,954

3 Claims. (Cl. 91-'443) This invention relates to a fluid servo system and more particularly to a servornotor which is capable of translating at various speeds. This constitutes a divisional application taken from my copending application No. 611,337, tiled September2l, 1956, yand entitled Fuel Control, now issued 'as United States Patent'No. 2,- 968,347.

lt is yan object of this invention to provide a means for regulating the speed of a servomotor so that it will move at a predetermined rate in one direction and at a selected increasedrate in the opposite direction.

lt still is a further object of this invention to-provide an ladjustment for varying the rate in which the servo piston will translate in one of its directions.

It is still a further object of this invention to provide ya time delay device which is characterized as being relatively simple in design and construction wherein a single valve functions to control the rate of movement of a servomotor in either direction of its movement.

` These and other objects of this invention Will become readily apparent from the following detailed description of the drawing:

A detailed description of a fuel control may be had by referring to the above-referred-to Patent No. 2,968,347. But suiiice it to say, the fuel is metered by throttle valve 134 and delivered to the engine through passage Sii. Fuel is delivered to the metering throttle valve through passages 42 and 1%2 which are connected to a source of high pressure fuel (not shown). The throttle valve has a pair Vof cooperating ports which are in rotational' `and rectilinear relationship with each other. The longitudinal motion is imparted by virtue or" piston 132 which is responsive to an engine operating variable sensed by bellows 13S. The engine operating variable, such as the pressure lof the air discharging from the compressor of the engine, is transmitted into cavity 186 through line 62. This pressure acts on the bellows which in turn transmits a proportional movement to lever 1%. This movement in turn varies the orice 196 which varies the pressure in line 64 downstream or orificerl. Thus, the pressure established between the variable orifice 196 and the fixed orifice 198 is proportional to the movement of bellows 18S which pressure is also transmitted to chamber 204 by line 262. Thus, the translation or" the port attached to piston 182 is proportional to the engine operating variable.

Rotational movement is imparted to the throttle valve 154 in response to the control shaft 22g and cam 226. The control shaft may be connected to the pilot lever in the cock pit of the aircraft (not shown). Movement of the cam 226 controls the movement of pilot valve 224 which in turn governs the application of duid into chamber 264 which causes translation of the servo piston 222. This translation is `converted into rotary movement by virtue of the linkage 212 which is connected to the throttle valve 1124. Pressurized servo fluid is directed through line 242 through the pilot valve 224 where it is metered and then directed to chamber 264 via passages 259 and 269 and passes through the time delay mechanism as will be more fully described herein below.

The pressure drop across throttle valve 104 is Vheld at a constant value by virtue 'of the pressure regulating valve 166. The pressure of theV fluid just upstream and downstream of throttle valve 1&4' are applied on either side of valve 106 and a spring 197 urges the valve closed. The pressure upstream of throttle valve 104 is directed to the valve 106 through passages 1032 and 1li/8 and the pressure downstream is directed to the opposing side via passages 50 and 11i). When the pressure drop exceeds a value as determined by the size of spring 107, the valve will open and conduct fluid upstream of the throttle valveV to drain. In this manner, the pressure drop is maintained at a constant value.

The single drawinggenerally shows a servo Isystem comprised of a pilot valve 224 and a servomotor 222. The pilot'valve essentially functions to direct high pressure fluid issuing from line 242 which is in communica-V tion witha source of high pressure servo fluid (not shown) to chamber 254 and communicates chamber 264 to drain `by way of annular passage 255 'and a restriction formed by theshculder 257 and thelbottom end of the sleeve 253. The pilot valve y-rnay be positioned upwardly or downwardly byvaction of cam 226 and lever 229 which in turn may be connected to la pilot lever. ln a fuel control application, for exampldwhich is intended to control the flow of fuel tothe combustion section of 'a turbine type of engine which is more fully disclosed in the above-mentioned patent, the pilot lever through the action of the servo device will position the throttle valve lil-4 so as to, provide the proper metering of fuel. rifhis serves to regulate the quantity of fuel being ldelivered to the engine. The time delay device is utilized to control the movement of the throttle valve so that the rate of fuel ydelivered to the engine will take different values depending whether the engine is in `an `accelerating `or decelerating operating regime. The throttle valve may also be controlled by other parameters for further regulation of thefuel. At this point it should be emphasized that any one skilledin the art will realize that ,the input signal and. the output response may be used for supplying power in accordance with an input signal of any variable for obtaining an output response for any other purpose withoutV departing from the scope of this invention.

In accordance with this invention, a hydraulic system is interposed between the servo control valve 224 and the servo piston 222 in order to provide for a controlled ratey of fuel dow increase and a more rapid rate of fuel flow decrease in response toV operation or" the pilots control lever. To this end, a time delay regulator system is provided. This regulator system includes avalve having a piston 232slidable in a sleeve 234 and urged to the right by a spring 236. A control chamber 24% is provided centrally of the piston 232 which receivesfiuid under suitable control pressure from the control valve 224.

High pressure fluid is directed to the control valve 224 by means of a line 242 to 'a port 244 at the control valve 224. When the valve stem 246 of the control valve 224 is moved downwardly, high pressure fluid from the port 244 is then conducted to the port 243 whereby it flows into the line 250 then to the chamber 252 of the regulator valve. From chamber 252 the fluid may pass to the port 259, annulus 256, port 25@ and then to the chamber 240 within the valve piston 232. Under theseconditions fluid under high pressure then Iflows to the right side of the valve into line 260 past la iixed oniice 262 and then to the chamber 264 on the bottom side of the servo piston 222. lt should be noted that the chamber 266 on the top side of the servo piston 222 is continuously exposed to high pressure uid from la line .268 leading from the line 242.

1n passing the orifice 262 -a pressure drop will be cre- Patented Nov. 12, 15563 l chamber 240.

against the action of the spring 2,80y which is located atk ated whereby a slightly lower pressure occurs in the chamber 264 as well as the passage 270 which leads around to the left-hand side of the regulator valve piston 232. From the line 270 iiuid can then enter a chamber 2,7 2 whereby pressure is exerted tending to moveV the valve piston 232 toward the right. Pressure in the chamber 272 in urging the piston 232 rtoward the right acts to permit further ow of high pressure tiuid to chamber 240 and the line 260. lf, for example, a pressure drop across the orifice '262 is 10 p.s.i. with a given supply pressure to the line 250 and the pressure in line 250 is suddenly increased, piston 232 will be urged to the left against the pressure of spring 236, tending to close oi port 259 thereby decreasing the pressure in chamber 240 until it reaches la'value 10 p.s.i. higher than that of the pressure in chamber 272. Following this, piston 232 will again move sufliciently to the right allowing the tlow to continue through the port 259, annulus 256, port 258, chamber 240, line 2160 and the chamberV 264 atrthe botto-m of the servo piston 222. Stated another way, if, for example, control valve 224 is displaced downward causing supply pressure from line 242 to be directed to line 260 through chamber 252, port 259, port 25S, and chamber 240, the

pressure drop across orifice 262 will exceed the pressure setting of spring 236 causing piston 232, the opposite ends of which are exposed to the pressures inlines 260 and 270, to move to theleft thereby reducing the area of port 259 with the attendant etect of throttling the flow Vfrom line 250 to line 260 until the pressure in l-ine 260 exceeds the pressure in line 270 by the amount `of the pressure setting of spring 236. With a given value of pressure drop across the orifice 262, it is then possible to establish the rate at which the servo piston 222 will move in an upward or increasedV fuel flow direction.

When the control valve 224 is moved in an upward direction, the port 248 is connected with ldrain so that liow in the line 250 is then reversed. This flow reversal begins at the chamber 264 at the bottom of the servo piston 222 so that the iluid attemptsto ow downwardly in line 260 past the restriction 262 and into Vthe chamber 240 of the piston 232. With a flow in this direction there is a pressure drop acnoss the restriction 262 whereby the pressure :in the line 270 and the chamber 272 at the left-hand side on the piston V232 is higher than the pressure in the This urges the piston 232 to the right rthe right-hand side of the valve piston 232. As the piston 232 moves to the right, it opens port 282 thereby opening chamber 272 to the line 250 and dnain. Fluid mayA now flow rapidly from the chamber 264 at the bottom of the servo piston 222 via the line 270, chamber 272, port 282 and then to the line 250. Thus, the restriction 262 is bypassed and the servo piston 222 can move down rapidly. A-s the servo piston 222 reaches its downward limit, the pressure in the chamber-264, line 270 and chamber 272 will reduce thereby permitting the piston 232 to move back toward the left to a neutral position.

Considering now the relationship of the time delay servo'with the control valve 224 and other system elements, it will be noted that the lever 229 is positioned at oneend by the control shaft cam 226 and at its other end 230 by spring 231 which preloads it against servo piston 222. The spring 231 which engages the left end 230 of the lever 229 is incorporated to insure the ability of the system to decrease fuel flow in case of sticking of the servo piston 222. In this event, pilot valve 224 bottoms against its sleeve to -act as a fulcrum for lever 229 permitting cam 226 to move the left end 230 of lever 229 downward thus freeing lever 230 hom the stuck piston 222 and lalso causing the throttle valve to move in the decreasing fuel ow direction. As will have beenrealized opposite sides `the tluid pressure upstream and downstream ci restriction of 262 serves to maintain the pressure drop across the restriction at a constant value. The force exerted by spring 236 determines the value of the pressure drop. It is apparentthat by selecting the position of screw adjustment 261, the force of the spring can be readily changed in order to effect a changein the value of the pressure drop. Since the pressure drop across 262 is held at a `constant value and since there is a fixed restriction, whose area is predetermined, then, of course, when servomotor 222 is being positioned upward, the ilow through the restriction 262 will be at a predetermined rate which in turn deter-mines the'rate at which servornotor 222 will translate.

'In summary then the throttle valve Visrpositioned inY j accordance with the pilots power lever position. However, with the time delay servo the throttle valve will be moved :to increase ttuel dlow at a given rate for power lever increase so that in case of a sudden increase'fuelV flowmovement of the power lever, an 'excessive rate of in-y crease in fuel ow is avoided. On the other hand, when from the foregoing, piston 232 which has acting of its the power lever is moved tov/ard :decrease fuel flow, the throttle valve and its servo are moved rapidly tow-ard decrease fuel flow.

Thus if the pilot moved his power lever to the 100% setting, then suddenly reduced the setting to 50% power and then again returned the power lever to the 100% setting rapidly, the fuel flow rate would immediately jump to the 100% setting if downward movement of the throttle servo piston 222 were very slow. For the instant when the power lever calledV for 50% power, the throttle valve would be set for such a liow through the action ofY the override spring 231, but when the power lever isV pushed up to the 100% setting, the throttle rotating servo Y piston 222, having already been at a high level from the thus be ineilective during this type of operation. `With rapid downward .movementof the throttle valve,. servo piston 222, this undesirable feature is eliminated.

What has been shown isa timedelay device which is formed by a single valve which serves to control the rate of movement of a servo piston such that the piston will move at a predetermined rate in one direction and at a selected rate in the opposite direction. The rate in which the piston will move in one of its directions can readily be selected by a mechanical adjusting device, and the rate in which the piston will move in the opposite direction will be selectively chosen by the proper positioning of the servo pilot valve.

I claim:

l. In a device having a servomotor, a source of fluid under pressure, a drain, a control valve for connecting one side of said servomotor to pressure or to drain and a time delay device connected between said valve and s aid servomortor, said time delay device including a restriction for slowing down the tiow of tluid to said servomotor, a second valve having a hollow piston therein, said hollowpiston being closed at one end and open at the other, a port controlled by said hollow piston normally connecting said restriction through the openend of said hollow piston with said 'control valve, an expansible chamber, said hollow piston forming one wall of Said chamber, a connection between 'said chamber and said servomotor, the pressure in said chamber when exceeding a predetermined pressure above the pressure within the hollow piston moving said hollow piston in a given direction and a second port in said second valve connecting said motor with drain through said control valveA when said hollow piston is so moved.

2. In a device having a servomotor, a source of uid under pressure, a drain, a control valve for connecting one side of said servomotor to pressure or to drain, a

, time delay device connected between said valve andV said second valve having a hollow piston therein, said hollow piston being closed at one end and open at the othea port in said hollow piston normally connecting said restriction through the open end of said hollow piston with said control valve, a chamber adjacent the closed end of said hollow piston, a connection between said chamber and said servomotor, the pressure in said chamber eX- ceeding the pressure in said hollow piston during movement of said servomotor in a given direction whereby said hollow piston is moved in a given direction, and a second port opened by movement of said hollow piston in said given direction for leading fluid from said connection to drain.

3. In a device having a servomotor, a source of fluid under pressure, a drain, a control valve for connecting one side or" said servomotor to pressure or to drain, a time delay device connected between said valve and said servomotor, said time delay device including a restriction for slowing down the How of iluid to said servornotor, a second valve having a hollow piston therein, said hollow piston being closed at one end and open at tne other, a port in said hollow piston normally connecting said restriction through the open end of said hollow pistonv with said control valve, a chamber adjacent the closed end of said hollow piston, a connection between said chamber and said servornotor, the pressure in said chamber exceeding the pressure in said hollow piston during movement of said servomotor in a given direction whereby said hollow piston is moved in a given direction, a second port opened by movement of said hollow piston in said given direction, and a connection between said second port and drain bypassing said restriction.

References Cited in the file of this patent UNITED STATES PATENTS 1,467,522 Amsler Sept. 11, 1923 1,972,462 Schafer Sept. 4, 1934 2,151,057 Suth Mar. 21, 1939 2,638,739 Barr May 19, 1953 2,807,279 Presnell Sept. 24, 1957 FOREIGN PATENTS 585,032 Great Britain l an. 29, 1947 OTHER REFERENCES Serial No. 366,840, Obstressal (AFRO), published Apr. 27, 1943. 

1. IN A DEVICE HAVING A SERVOMOTOR, A SOURCE OF FLUID UNDER PRESSURE, A DRAIN, A CONTROL VALVE FOR CONNECTING ONE SIDE OF SAID SERVOMOTOR TO PRESSURE OR TO DRAIN AND A TIME DELAY DEVICE CONNECTED BETWEEN SAID VALVE AND SAID SERVOMOTOR, SAID TIME DELAY DEVICE INCLUDING A RESTRICTION FOR SLOWING DOWN THE FLOW OF FLUID TO SAID SERVOMOTOR, A SECOND VALVE HAVING A HOLLOW PISTON THEREIN, SAID HOLLOW PISTON BEING CLOSED AT ONE END AND OPEN AT THE OTHER, A PORT CONTROLLED BY SAID HOLLOW PISTON NORMALLY CONNECTING SAID RESTRICTION THROUGH THE OPEN END 